7.5 Alcohol and Other Carcinogens

A free GCSE Biology lesson for AQA (8461) from OBA School: short- and long-term effects of alcohol, alcohol in pregnancy, units, and carcinogens including ionising radiation. Watch the video, read the explanation and worked examples, then try the revision questions. You can work through the full lesson, with every video, practice quizzes and printable worksheets with mark schemes, in our free online course.

What you will learn

• Describe the short-term and long-term effects of alcohol on the body, including the liver and brain
• Explain how drinking alcohol in pregnancy can harm the unborn baby
• Calculate units of alcohol and compare them with health guidelines
• Describe carcinogens, including ionising radiation, as risk factors for cancer

Key words

• Alcohol: Ethanol: a drug that slows down the nervous system. It is a toxin broken down by the liver.
• Unit of alcohol: 10 ml (8 g) of pure alcohol. Units = strength (% ABV) × volume (ml) ÷ 1000.
• Cirrhosis: Permanent scarring of the liver, so it can no longer work properly.
• FASD: Fetal alcohol spectrum disorder: lifelong problems in a child caused by alcohol drunk during pregnancy.
• Carcinogen: Anything that increases the risk of cancer.
• Ionising radiation: High-energy radiation, such as UV, X-rays, gamma rays and radiation from radon gas, that can damage DNA.

The effects of alcohol

Alcohol (ethanol) is absorbed into the blood from the stomach and small intestine and reaches every organ. It is a toxin, broken down mainly by the liver.

• Short term; Effects slows down the nervous system: slower reactions, poor coordination and judgement, so accidents are more likely; large amounts can cause unconsciousness, coma or death
• Long term: liver; Effects liver cells are damaged as they break down alcohol: fatty liver, then cirrhosis (scarring) and liver cancer
• Long term: brain; Effects brain damage, memory loss and mental health problems
• Other; Effects raised blood pressure and heart disease; cancers of the mouth, throat, oesophagus and breast

Key fact: The more alcohol people drink, the higher the risk. The causal mechanism is known: the liver is damaged as it breaks down the alcohol.

Alcohol in pregnancy

Alcohol passes from the mother's blood across the placenta into the blood of the fetus, whose liver cannot break it down well. It can cause miscarriage, stillbirth, premature birth and low birth weight, and fetal alcohol spectrum disorder (FASD): problems with growth, learning, memory and behaviour that last for life.

Key fact: UK health advice is that the safest approach in pregnancy is not to drink alcohol at all.

Units of alcohol

units = strength (% ABV) × volume (ml) ÷ 1000

UK guideline for adults: no more than 14 units a week, spread over three or more days.

Worked example: units in a drink

A 330 ml can of cider is 4.5% alcohol by volume (ABV). How many units does it contain?
units = 4.5 × 330 ÷ 1000 = 1.485

Answer: about 1.5 units

Worked example: a week of drinking

Sam drinks three 250 ml glasses of 12% wine each weekend. Is this within the guideline?
one glass = 12 × 250 ÷ 1000 = 3 units, so three glasses = 9 units

Answer: 9 units a week, within 14 – but all on one weekend, not spread over 3 or more days

Carcinogens and ionising radiation

A carcinogen is anything that increases the risk of cancer, usually by causing mutations in the DNA of cells. Examples include chemicals in tobacco smoke, asbestos fibres and ionising radiation.

• UV light from the sun and sunbeds; Cancer risk skin cancer (melanoma); Reducing the risk sunscreen, covering up, avoiding sunburn and sunbeds
• Radon gas from rocks in some areas; Cancer risk lung cancer; Reducing the risk test homes; improve ventilation under floors
• X-rays and gamma rays in medicine; Cancer risk small increased risk; Reducing the risk used only when the benefit outweighs the risk; staff are shielded

Exam tip: Exposure to carcinogens is a risk factor: it increases the chance of cancer. The larger the dose and the longer the exposure, the greater the risk.

Common mistakes

• Saying alcohol is a stimulant. It is a depressant: it slows down the nervous system.
• Forgetting to divide by 1000 in the units formula, or using the volume in litres instead of ml.
• Saying alcohol in pregnancy only affects the mother. It crosses the placenta into the fetus.
• Saying all radiation is ionising. Visible light and radio waves are not; UV, X-rays and gamma rays are.

Revision questions

Try these, then check your answers below each one.

Question 1. Units = strength (% ABV) × volume (ml) ÷ 1000. How many units are in a 500 ml bottle of 5% beer?

Answer: 2.5

Working: 5 × 500 ÷ 1000 = 2.5 units.

Question 2. Which organ is most damaged by long-term heavy drinking? (Choose from: Lungs, Skin, Bones, Liver.)

Answer: Liver

Working: The liver breaks down alcohol and is damaged in the process: fatty liver, cirrhosis and liver cancer.

Question 3. True or false? Alcohol is a stimulant that speeds up reactions.

Answer: False

Working: False. Alcohol is a depressant: it slows down the nervous system and reactions.

Related lessons

• Previous lesson: 7.4 Diet, Exercise, and Disease
• Next lesson: 8.1 Photosynthesis
• In this chapter: 7.1 Non-Communicable Diseases
• In this chapter: 7.2 Cancer
• In this chapter: 7.3 Smoking and the Risk of Disease

Continue in the full course

This lesson is section 7.5 (AGCBH0705) of our free GCSE Biology course for AQA. In the full course you get every video for this section, a self-marking practice quiz, a printable worksheet with a mark scheme, chapter tests, and your progress saved. Go to the full GCSE Biology course.